Pulmonary lesions induced by SARS-CoV-2 infection in domestic cats

Natural SARS-CoV-2 infection in dogs: Determination of viral loads, distributions, localizations, and pathology

Instances of reverse zoonosis involving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been documented in both controlled experiments and spontaneous cases. Although dogs are susceptible to infection, clinical significance is limited to mild or asymptomatic. Here, we investigate the fatal cases of natural SARS-CoV-2 infection in dogs in Thailand. Pathological findings of SARS-CoV-2-infected dogs reveal severe diffuse alveolar damage, pulmonary hyalinization and fibrosis, and syncytial formation, together with minor lesions in brain and kidney. Employing reverse transcription-digital PCR, substantial viral loads of SARS-CoV-2 were detected in lung, kidney, brain, trachea, tonsil, tracheobronchial lymph node, liver, and intestine, respectively. Localization of SARS-CoV-2 within various tissues was examined through immunohistochemistry (IHC), where the co-localization of the viral spike protein and the angiotensin-converting enzyme 2 (ACE2) receptor was illustrated using double IHC. SARS-CoV-2 localization was markedly identified in the epithelial cells of the lung, trachea, intestine and kidneys, and moderately presented in the salivary gland and gall bladder, where the co-localization with the ACE2 was also evident. Neurons in the brainstem where exhibited lymphocytic perivascular cuffing were also found to be positive for SARS-CoV-2 in IHC testing, despite lacking ACE2 receptor expression. In addition, SARS-CoV-2 replication within the lungs of infected dogs was confirmed by transmission electron microscopy, visualizing free viral particles within the cytosol or the endoplasmic reticulum of syncytial cells within the lung. This study considerably expanded on the knowledge of the pathology associated with natural SARS-CoV-2 infection in dogs, a scenario that is relatively infrequent but occasionally leads to fatal outcome. Furthermore, these findings suggest the potential utility of dogs as a model for studying SARS-CoV-2 infection in humans, warranting further investigation.

Neurologic Effects of SARS-CoV-2 Transmitted among Dogs

SARS-CoV-2 induces illness and death in humans by causing systemic infections. Evidence suggests that SARS-CoV-2 can induce brain pathology in humans and other hosts. In this study, we used a canine transmission model to examine histopathologic changes in the brains of dogs infected with SARS-CoV-2. We observed substantial brain pathology in SARS-CoV-2-infected dogs, particularly involving blood-brain barrier damage resembling small vessel disease, including changes in tight junction proteins, reduced laminin levels, and decreased pericyte coverage. Furthermore, we detected phosphorylated tau, a marker of neurodegenerative disease, indicating a potential link between SARS-CoV-2-associated small vessel disease and neurodegeneration. Our findings of degenerative changes in the dog brain during SARS-CoV-2 infection emphasize the potential for transmission to other hosts and induction of similar signs and symptoms. The dynamic brain changes in dogs highlight that even asymptomatic individuals infected with SARS-CoV-2 may develop neuropathologic changes in the brain.

Infection Dynamics, Pathogenesis, and Immunity to SARS-CoV-2 in Naturally Susceptible Animal Species

SARS-CoV-2, the causative agent of the COVID-19 pandemic, presents a broad host range. Domestic cats and white-tailed deer (WTD) are particularly susceptible to SARS-CoV-2 with multiple variant strains being associated with infections in these species. The virus replicates in the upper respiratory tract and in associated lymphoid tissues, and it is shed through oral and nasal secretions, which leads to efficient transmission of the virus to contact animals. Robust cell-mediated and humoral immune responses are induced upon infection in domestic cats, which curb the progression of clinical disease and are associated with control of infection. In WTD, high levels of neutralizing Abs are detected early upon infection. In this review, the current understanding of the infection dynamics, pathogenesis, and immune responses to SARS-CoV-2 infection in animals, with special focus on naturally susceptible felids and WTD, are discussed.

Comparison of Cardiovascular Pathology In Animal Models of SARS-CoV-2 Infection: Recommendations Regarding Standardization of Research Methods

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged as the viral pathogen that led to the global COVID-19 pandemic that began in late 2019. Because SARS-CoV-2 primarily causes a respiratory disease, much research conducted to date has focused on the respiratory system. However, SARS-CoV-2 infection also affects other organ systems, including the cardiovascular system. In this critical analysis of published data, we evaluate the evidence of cardiovascular pathology in human patients and animals. Overall, we find that the presence or absence of cardiovascular pathology is reported infrequently in both human autopsy studies and animal models of SARS-CoV-2 infection. Moreover, in those studies that have reported cardiovascular pathology, we identified issues in their design and execution that reduce confidence in the conclusions regarding SARS-CoV-2 infection as a cause of significant cardiovascular pathology. Throughout this overview, we expand on these limitations and provide recommendations to ensure a high level of scientific rigor and reproducibility.

Animal models and SARS-CoV-2-induced pulmonary and neurological injuries

Laboratory animals are essential mainly for experiments aiming to study pathogenesis and evaluate antivirals and vaccines against emerging human infectious diseases. Preclinical studies of coronavirus disease 19 (COVID-19) pathogenesis have used several animal species as models: transgenic human ACE2 mice (K18 mice), inbred BALB/c or C57BL/6N mice, ferrets, minks, domestic cats and dogs, hamsters, and macaques. However, the choice of an animal model relies on several limitations. Besides the host susceptibility, the researcher's experience with animal model management and the correct interpretation of clinical and laboratory records are crucial to succeed in preclinical translational research. Here, we summarise pathological and clinical findings correlated with virological data and immunological changes observed from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) experimental infections using different well-established SARS-CoV-2 animal model species. This essay aims to critically evaluate the current state of animal model translation to clinical data, as described in the human SARS-CoV-2 infection.

Feline pulmonary hypertension: are we overlooking an important comorbidity?

Pulmonary hypertension (PH) is a potential complication in many disease states, yet it has been largely overlooked in feline medicine. Recently, increased awareness of potential underlying causes has led to a wider understanding of the disease process in humans, with a focus on tailoring therapy to include specific treatment of the underlying etiology. Most of these treatments are not yet available in veterinary medicine, but as they move from the human to the veterinary field, it would be beneficial to better understand the forms of PH encountered in different species. Recently, diagnosis and classification of PH in dogs has been the focus of an American College of Veterinary Internal Medicine consensus statement, yet this condition has received little attention in cats. It is therefore our intention to raise awareness of this condition in cats and to propose a classification system for the types of PH seen in feline patients. As new medications are developed for the treatment of PH, it is important to recognize which forms of PH are seen in feline patients and understand the etiology of the disease. There are many reports of PH (or suspected PH based on echocardiographic assessment) in cats. In this review, we highlight the large number of conditions, and different etiologies, that are associated with PH. Improving understanding of this condition will bring us closer to being able to investigate the benefits of potential new diagnostics and therapies as they become available.

Risk Factors for SARS-CoV-2 Infection and Illness in Cats and Dogs1

We tested swab specimens from pets in households in Ontario, Canada, with human COVID-19 cases by quantitative PCR for SARS-CoV-2 and surveyed pet owners for risk factors associated with infection and seropositivity. We tested serum samples for spike protein IgG and IgM in household pets and also in animals from shelters and low-cost neuter clinics. Among household pets, 2% (1/49) of swab specimens from dogs and 7.7% (5/65) from cats were PCR positive, but 41% of dog serum samples and 52% of cat serum samples were positive for SARS-CoV-2 IgG or IgM. The likelihood of SARS-CoV-2 seropositivity in pet samples was higher for cats but not dogs that slept on owners’ beds and for dogs and cats that contracted a new illness. Seropositivity in neuter-clinic samples was 16% (35/221); in shelter samples, 9.3% (7/75). Our findings indicate a high likelihood for pets in households of humans with COVID-19 to seroconvert and become ill.